Apparatus for forming the head on a flat head screw



Feb. 21, 1967 R. c. ELLSWORTH 3,304,561

APPARATUS FOR FORMING THE HEAD ON A FLAT HEAD SCREW Filed Sept. 18, 1964 I NVENTOR. 54

Roberr C. Ellsworrh ATTORNEY United States Patent 3,304,561 APPARATUS FOR FORMING THE HEAD ON A FLAT HEAD SCREW Robert C. Ellsworth, Pacific Palisades, Calif., assignor to American Fastener Corporation, New York, N.Y., a corporation of Nevada Filed Sept. 18, 1964, Ser. No. 397,449 4 Claims. (Cl. 10-7) This invention relates to the manufacture of fiat head screws and more particularly to the construction of apparatus for use in forming a cruciform recess combined wit-h a slot fully extending across the entire surface of a flat head screw, and to the method of operation employed in forming such combined cruciform recess and transverse fully-extending slot.

An object of this invention is to provide an improved form of punch and a cooperating die to produce a combination slot and recess in a screw head formed between the two so that the slot will be formed across the entire top of the head by defining a limiting region from which the upset metal is excluded in the formation of the head.

Another object of the invention is to provide an apparatus for forming a head on a cylindrical blank, wherein a punch and die are provided with cooperating elements that form the head and a slot in the head, in such man ner that the upset material that is to form the head is confined entirely within a chamber in the die so that no fins or burrs are formed on the head.

In' accordance with a preferred embodiment of the invention, a punch and die are provided with the punch embodying a diametrically disposed vane to fit between two diametrically spaced lugs in the die so the space occopied by the punch vane between the two cooperating spaced lugs defines a region from which upset head-forming metal will be excluded, and such region will serve to define a slot extending across the entire surface of the head when the screw is completely finished.

A feature of the invention is a punch having a cruciform portion with the vane in alignment with one pair of wings of the cruciform portion to form a combination cruciform recess and fully-extending slot in the head.

These and other objects, features and advantages of the apparatus and method invention are described in the following detailed specification and the accompanying drawing, in which:

FIGURE 1 is a side elevation view, partially in section, showing the punch and the die of the preferred embodiment of the invention, set in separated positions;

FIGURE 2 is a side elevational view of a typical shape of a screw blank after it has been struck its first coning blow;

FIGURE 3 is a sectional view of the blank in the die of FIGURE 1 with the punch about half way down on the second blow;

FIGURE 4 is a view similar to FIGURE 3 with the punch shown about three-quarters of the way down and illustrates the manner in which the metal is upset by the punch and caused to flow outwardlyand upwardly to fill the head forming chamber of the die;

FIGURE 5 is a view similar to FIGURE 1, with the punch and the die in substantially closed position, to show the manner in which the upset metal of the blank is caused to flow outwards and upwards to fill the chamber completely and thereby form the flat head on the screw, with the blade of the punch and the lugs of the die aligned and cooperating to constitute a region of exclusion, to prevent the upset metal from entering such region, thereby serving to have such region of exclusion become the slot in the finished screw head;

3,304,561 Patented Feb. 21, 1967 ice FIGURE 6 is a plan view of the recess and head forming apparatus of FIGURE 1;

FIGURE 7 is a bottom plan view of the punch of FIG- URE 1; and

FIGURE 8 is a plan view of the formed recess in the head of a flat head screw.

As shown in FIGURE 1, the two main elements of the die set are a stationary anvil or die 12 and reciprocating hammer 14 having punch 15. The die 12 is provided wit-h a central bore 16 for accommodating and closely guiding a wire 18 (FIG. 3) from which the screw shank and the head for a screw are to be formed. The forward or upper end of the bore 16 is divergin-gly enlarged conically and uniformly to define a frusto-conical chamber 20 (FIG. 6) which will define the size and shape of the underside of the head to be formed at the forward end of the wire 18.

Two lugs 24 and 26 are integrally formed on or attached to the conical wall 27 that defines the head-shaping chamber 26. The two lugs 24 and 26 serve to define the outer end spaces of a region that will constitute the ultimate slot that is to be formed in the screw head that will be shaped on the upper end of the wire 18 in accordance with the shape and dimensions of the head-shaping chamber 20 in the die 12.

The two lugs 24 and 26 are relatively thin according to the lateral width of the slot which they are to define. The two lugs 24 and 26 are disposed diametrically opposite each other, with their corespective side surfaces in co-planar disposition and with their inner end walls 24A and 26A (FIG. 1) and side wall surfaces 24B and 26B disposed to be slightly inclined or divergent from a central axis 29 of the bore 16 to provide slight draft that will permit easy insertion and withdrawal of a cooperating blade or vane 30 of punch 15 and ejection of the finished blank. Their upper surfaces 240 and 26C are coplanar with the upper surface of the die 12.

The cooperating vane 30 is part of punch 15 and is carried on and actuable by the reciprocating hammer 14. The punch 15 strikes axially against the wire blank 18 to upset the metal of that blank 18 (FIGS. 3 and 4) and to cause such upset metal to flow into the available space in the head-shaping chamber 20, to thereby assure the formation and shaping of the flat head for the screw blank. The vane 39 extends axially from the hammer 14 (FIG. 1) a distance equal to or slightly less than the height of the inner end walls 24A and 26A of the respective lugs 24 and 26.

The die 12 and punch 15 are suitable for use in a twoblow heading machine, in which the first blow upsets the upper end of the wire 18 to cause an initial bulging effect, typically as shown in FIGURE 2, that will partially form the lateral dispersion of metal for the screw head.

The punch 15 (FIG. 1 and 7) comprises a main central punch proper having two pairs of oppositely disposed wings 15A at right angles to each other and arranged in cruciform disposition with the lower ends of the wings 15A merging to constitute a bottom of multi-planar shape, to form a standard Phillips-type recess in the screw. The vane 30 constitutes part of the punch 15, although it may be made as a separate element and then suitably mechanically combined with the cruciform part of punch 15 to provide the space-filling function between lugs 24 and 26 for which it is intended.

The width of vane 30 equals the width of the standard cruciform vane and its side walls 30A are angled the same extent as the angles of the facets of the standard cruciform vane.

As indicated in FIGURE 2, the first blow of the punch causes the top end of the wire to bulge and upset to form the typical initial lateral dispersion 34 of the metal for the head of the screw. The second blow of the punch upsets the wire 18 still further as in FIGURE 3, and causes the upset metal in the bulge 34 to spread further outwardly and radially into the annular region surrounding the punch 15 in the chamber 20, with the upset metal flowing outwardly and upwardly around the punch and into the space between the punch and the side wall 27 of the chamber 20 to form annular bulge 36.

As the punch 15 moves progressively downward during the second blow, the punch 15 (FIG. 4) is forced further downward into the metal of the blank 18 and forces the metal of the annular bulge 36 to flow still further outward and upward to fill all the available space within the chamber 20, encircling the punch 15 and extending to the side surfaces of the two lugs 24 and 26, and to the side surfaces of the vane 30, which is then in alignment and in substantially sliding contact with lugs 24 and 26 along their interedge surfaces, as shown in FIGURE 5. When the hammer 14 and punch 15 are fully engaged with the die 12, the upper surfaces 24C and 26C (FIG. 1) of the lugs 24 and 26 are in contact with the lower surface 14A of hammer 14, and the side surfaces 30A of vane 30 are coplanar with the side surfaces 24B and 26B of lugs 24 and 26. Any metal that may be extruded upwardly along the faces of lugs 24 and 26 prior to the arrival of vane 30 will be pressed back down by vane 30 as it progresses towards the end of its stroke.

The hammer 14 and the die 12 are provided with suitable guide means to keep the two dies in alignment and to prevent circular twisting. Such guide means comprise the locating pins 42 and 44 (FIGS. 1 and 5) which cooper-ate with cooperating pilots or guide holes 42A and 44A, to hold the hammer 14 and the die 12 in proper alignment during set-up and operation. However, the locating pins 42 and 44 may be removed after the hammer 14 and die 12 are properly aligned prior to operation.

The stroke or extent of downward movement of the movable hammer member 14 for control of the stroke of the punch 15 is suitably controlled on the operating machine and need not be described herein, since that part of the control operation of such machinery is well known.

After the complete forming operation of the head on the blank 18 the hammer 14 is raised to provide an ejection space for the formed blank 18, and ejection means (not shown) is suitably actuated by the equipment to remove the formed blank 18 from the bore 16 of the die 12.

The head of the formed blank, when viewed from the top, will be as seen in FIGURE 8, in which the central recess is of cruciform shape as represented at 52, and in which the slot 54 extends completely across the full width of the head 22 thus formed.

As will be seen upon referring to FIGURES 1, 5 and 6, the vane 30 and the two side lugs 24 and 26 provide a region of exclusion, from which the upset metal is excluded as such metal is forced outwardly and upwardly into the available free space in the chamber 20, around the punch 15, to form slot 54 without fins or burrs hecause the upset material chamber 20.

While the details and the description have been shown with the elements arranged in position with respect to a vertical operating axis, the machine and elements are generally arranged with the axis of the equpiment disposed in a horizontal direction, so that an ejected blank may more readily be dropped out of the die in which it has been formed.

While a preferred form of the embodiment of the invention has been shown, in the screw head and in the method and apparatus for shaping it, minor changes may be made without departing from the spirit and scope of the invention as set forth in the claims.

is confined entirely within the What is claimed is: 1. Apparatus for shaping a flat head on a screw blank comprising:

a die and a hammer having a cooperating punch; said die having a flat top surface and an axial bore extending inward from said surface to receive a blank whose top end is to be shaped into a head having a slot extending across the entire top of the head for receiving the bit of a screw driver, said die having a chamber end of said bore of inverted, truncated, conical shape with a wall terminating at said surface to define the outer contour limits of the head to be formed on said blank; said die also having two integral lugs extending radially inwardly and co-planarly from two diametrically opposite areas of said wall which defines said chamber, with the upper surface of each of said lugs coplanar with the upper surface of said die and the inner surface of each of said lugs exteinding axially into said chamber a distance substantially equal to the depth of the outer ends of the slot to be formed;

said cooperating punch having a fiat bottom surface and a transverse vane axially extending from said bottom surface, said transverse vane centered on and extending laterally from the axis of said punch toward the outer edges of said punch and shaped to be substantially co-planar with the side surfaces of said lugs and in substantially sliding contact with the inner surfaces of said lugs when said punch fully engages said die, said vane extending axially from said flat bottom surface a uniform distance along its length, the distance being substantially equal to the depth of the outer ends of the slot to be formed such that when said die and hammer are in opposed contacting relation the transverse vane of the punch and the lugs will be in alignment and said flat top and bottom surfaces co-planar to define a closed region from which the upset head-forming metal of said blank will be excluded to thereby define a conical region and further define a slot across the entire upset head of the blank.

2. The apparatus of claim 1 wherein said punch further comprises a cruciform portion having one pair of wings in alignment with said vane and a second pair of wings at right angles to said vane, the width of said wings being substantially equal to the width of said vane.

3. The apparatus of claim 1 wherein said hammer and said die include cooperating guide means for aligning said vane of said punch with said lugs of said die.

4. The apparatus of claim 2 wherein said hammer comprises locating means extending axially from said hammer, and said die comprises guide holes in its upper surface for engagement with said locating means, said locating means and said guide holes being positioned such that when engaged said vane of said punch is in alignment with said lugs of said die.

References Cited by the Examiner UNITED STATES PATENTS 162,642 4/1875 Frearson 10--10 452,064 5/1891 Rogers 10-7 1,491,464 4/1924 Coomer 83--637 1,910,182 5/1933 Robertson 8545 2,359,898 10/1944 Clark 85--45 3,166,769 1/1965 Wieber 1010 3,177,506 4/1965 De Vellier 10-7 FOREIGN PATENTS 1,362,922 4/1964 France.

CARL W. TOMLIN, Primary Examiner. R. S. BRITTS, Assistant Examiner. 

1. APPARATUS FOR SHAPING A FLAT HEAD ON A SCREW BLANK COMPRISING: A DIE AND A HAMMER HAVING A COOPERATING PUNCH; SAID DIE HAVING A FLAT TOP SURFACE AND AN AXIAL BORE EXTENDING INWARD FROM SAID SURFACE TO RECEIVE A BLANK WHOSE TOP END IS TO BE SHAPED INTO A HEAD HAVING A SLOT EXTENDING ACROSS THE ENTIRE TOP OF THE HEAD FOR RECEIVING THE BIT OF A SCREW DRIVER, SAID DIE HAVING A CHAMBER END OF SAID BORE OF INVERTED, TRUNCATED, CONICAL SHAPE WITH A WALL TERMINATING AT SAID SURFACE TO DEFINE THE OUTER CONTOUR LIMITS OF THE HEAD TO BE FORMED ON SAID BLANK; SAID DIE ALSO HAVING TWO INTEGRAL LUGS EXTENDING RADIALLY INWARDLY AND CO-PLANARLY FROM TWO DIAMETRICALLY OPPOSITE AREAS OF SAID WALL WHICH DEFINES SAID CHAMBER, WITH THE UPPER SURFACE OF EACH OF SAID LUGS COPLANAR WITH THE UPPER SURFACE OF SAID DIE AND THE INNER SURFACE OF EACH OF SAID LUGS EXTENDING AXIALLY INTO SAID CHAMBER A DISTANCE SUBSTANTIALLY EQUAL TO THE DEPTH OF THE OUTER ENDS OF THE SLOT TO BE FORMED; SAID COOPERATING PUNCH HAVING A FLAT BOTTOM SURFACE AND A TRANSVERSE VANE AXIALLY EXTENDING FROM SAID BOTTOM SURFACE, SAID TRANSVERSE VANE CENTERED ON AND EXTENDING LATERALLY FROM THE AXIS OF SAID PUNCH TOWARD THE OUTER EDGES OF SAID PUNCH AND SHAPED TO BE SUBSTANTIALLY CO-PLANAR WITH THE SIDE SURFACES OF SAID LUGS AND IN SUBSTANTIALLY SLIDING CONTACT WITH THE INNER SURFACES OF SAID LUGS WHEN SAID PUNCH FULLY ENGAGES SAID DIE, SAID VANE EXTENDING AXIALLY FROM SAID FLAT BOTTOM SURFACE A UNIFORM DISTANCE ALONG ITS LENGTH, THE DISTANCE BEING SUBSTANTIALLY EQUAL TO THE DEPTH OF THE OUTER ENDS OF THE SLOT TO BE FORMED SUCH THAT WHEN SAID DIE AND HAMMER ARE IN OPPOSED CONTACTING RELATION THE TRANSVERSE VANE OF THE PUNCH AND THE LUGS WILL BE IN ALIGNMENT AND SAID FLAT TOP AND BOTTOM SURFACES CO-PLANAR TO DEFINE A CLOSED REGION FROM WHICH THE UPSET HEAD-FORMING METAL OF SAID BLANK WILL BE EXCLUDED TO THEREBY DEFINE A CONICAL REGION AND FURTHER DEFINE A SLOT ACROSS THE ENTIRE UPSET HEAD OF THE BLANK. 